If the Democrats want to really rattle Trump during the debates, they need to run a quick-witted woman (nothing offends him more than women who are better than him at anything), especially one that is not afraid to go toe-to-toe with him. Better yet, one who served so they can call him out for a being a pussy, question whether his penis was the bone spur (emphasis on the spur) in question, and when referred to as a "nasty" woman (Trump really is weak on insults), respond by saying she can't be THAT nasty since she hasn't slept with Trump, not even for money.
People think Trump is a good troll and full of insults. Let me tell you - he is a rank amateur. Problem is that his opponents really aren't very good at it either. Hillary just had that simpering grin. That's not enough. Trump will slink away if truly confronted - bullies always do. And it would be funny to watch him cry on the national debate stage.